Package-on-package (POP) assemblies are emerging to combine package substrates that have one or more dies mounted on the respective package substrates to provide a higher component density in electronic devices such as, for example, mobile computing devices. Present POP assemblies may incorporate an interposer or similar substrate between the package substrates of a POP assembly to facilitate routing of electrical signals between dies of the package substrates. However, the interposer may increase a dimension (e.g., a Z-direction) of a POP assembly in a direction perpendicular to package substrate surfaces (e.g., X and Y directions) having the one or more dies mounted thereon. Currently, there is pressure to decrease the dimensions of the POP assembly to accommodate smaller mobile computing devices by eliminating the interposer.
One emerging solution utilizes the formation of vias in a mold compound to route electrical signals between package substrates of a POP assembly. The mold material may be deposited on a package substrate and, subsequently, a laser drilling process may be used to form vias through the mold material. However, the laser drilling process may be a costly additional operation due to the extensive time of the laser drilling and/or the additional operational step/equipment needed in a manufacturing setting to support the laser drilling. Additionally, laser drilling may provide vias having a conical profile with sloped sidewalls that may increase a likelihood that solderable material at a top portion of the laser-drilled vias will bridge and cause shorting of interconnect structures formed by the solderable material. Such likelihood of bridging in laser-drilled vias may increase as interconnect structures increase in density with smaller pitch between the interconnect structures to provide a smaller form factor of a POP assembly.